Rotary apparatus with fluid blast means for making glass fibers from heat-softenable mineral materials

ABSTRACT

THE DISCLOSURE EMBRACES A METHOD OF AND APPARATUS FOR PROCESSING HEAT-SOFTENABLE MINERAL MATERIALS, SUCH AS GLASS, AND INVOLVES DELIVERING PRIMARY FILAMENTS BY CENTRIFUGAL FORCES FROM A SPINNER INTO A GASEOUS BLAST WHICH ATTENUATES THE PRIMARY FILAMENTS INTO FIBERS. THE APPARATUS INCLUDES A BLOWER CONTROL SURFACE FASHIONED WITH A RECESS OR ZONE CONFIGURATED TO ESTABLISH TURBULENCE AT A REGION TO PROMOTE FRACTURE OF LONGER FIBERS INTO SHORTER LENGTH FIBERS, THE LATTER BEING PARTICULARLY USEFUL IN FORMING HIGH DENSITY FIBROUS PRODUCTS.

Fe. 2, 1971 D. KLEIST 3,560,179

ROTARY APPARATUS WITH FLUID BLAST MEANS FOR MAKING GLASS FIBERS FROM HEAT-SOFTENABLE MINERAL MATERIALS Filed July 9, 1968 3 Sheets-Sheet 1 INVENTOR.

WIQM @h 2, 1%?1 KLEIST 3,560,179

ROTARY APPARATUS WITH FLUID BLAST MEANS FOR MAKING GLASS FIBERS FROM HEAT-SOFTENABLE MINERAL MATERIALS Filed July 9, 1968 3 Sheets-Sheet 2 INVENTOR.

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ROTARY APPARATUS WITH FLUID BLAST MEANS FOR KING GLASS FIBERS FROM HEAT-SOFTENABLE MINERAL MAT ALS Filed July 9, 1968 3 Sheets-Sheet 3 INVENTOR.

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United States Patent Olfice 3,556,179 Patented Feb. 2, 1971 3,560,179 ROTARY APPARATUS WITH FLUID BLAST MEANS FOR MAKING GLASS FIBERS FROM HEAT- SOFTENABLE MINERAL MATERIALS Dale Kleist, St. Louisville, Ghio, assignor to Owens- Corning Fiberglas Corporation, a corporation of Delaware Filed July 9, 1968, Ser. No. 743,545 Int. Cl. C031) 37/04, 37/06 US. Cl. 6514 4 Claims ABSTRACT OF THE DISCLOSURE The disclosure embraces a method of and apparatus for processing heat-softenable mineral materials, such as glass, and involves delivering primary filaments by centrifugal forces from a spinner into a gaseous blast which attenuates the primary filaments into fibers. The apparatus includes a blower control surface fashioned with a recess or zone configurated to establish turbulence at a region to promote fracture of longer fibers into shorter length fibers, the latter being particularly useful in forming high density fibrous products.

This invention relates to method of and apparatus for processing heat-softenable mineral materials, such as glass, and more especially to a method and arrangement for projecting a large number of linear bodies or primary filaments of glass from orifices in a wall of a rotating hollow spinner by centrifugal forces, and engaging the bodies or primary filaments by a gaseous attenuating blast under conditions whereby the linear bodies or primary filaments are attenuated into fibers of comparatively short length.

Glass fibers have been produced by delivering primary filaments of glass through an orificed peripheral wall of a rotating spinner or rotor and engaging the primary filaments or bodies by a gaseous blast of compressed air or steam thereby attenuating the bodies or primary filaments to fibers of varying lengths. For most end uses of the fibers it has been desirable that a large percentage of the attenuated fibers be of substantial length to lend flexibility and resiliency to a mass or mat of the collected fibers. Such longer fibers are desirable in insulating mats or batts usually of low densities of from one to three pounds per cubic foot. Where fibers attenuated by such method are collected in a mass and the mass compressed in the formation of high density products, such as formboards, wall boards, roof boards and the like, which are of densities upwards of twelve pounds or more per cubic foot, the fibers should be of comparatively short length as the short length fibers function as columns or struts in the end product to provide a high strength product. Where the fiber mass utilized for forming high density products contains fibers of substantial length, the longer fibers are of more flexible and resilient character and, in a high density end product, the longer fibers tend to lower the strength of the product because the longer fibers do not provide a structural column or strut effect in a high density product.

The present invention embraces a method of attenuating primary filaments or linear bodies of heat-softenable material, such as glass, wherein turbulence is established by a control surface in regions of the gaseous blast, the turbulence promoting the fracture of longer fibers into shorter length fibers.

An object of the invention resides in a method of forming primary filaments or bodies of glass by centrifuging the glass from orifices in the wall of a rotating spinner, and controlling an attenuating blast engaging the primary filaments whereby long fibers attenuated from the primary filaments are caused to impinge a blast guiding or confining surface in a manner to fracture the long fibers into short length fibers.

Another object of the invention resides in a special configuration of a control or guide surface for a high velocity fiber attenuating blast whereby turbulence is established in a region of the gaseous blast adjacent the blast guiding surface whereby, under the influence of the turbulence set up in the attenuating blast, the longer fibers are impinged against the blast control or guide surface to fracture the longer fibers into short length fibers.

Another object of the invention resides in an apparatus for attenuating centrifuged bodies or primary filaments of glass into fibers through the use of a high velocity,

" gaseous attenuating blast delivered along a guide surface of the blower skirt, the surface being fashioned with a recess or zone providing a region of reduced pressure for establishing turbulence in the blast whereby the longer fibers are fracture to provide comparatively short length fibers of a character suitable for the fabrication of high density, high strength products.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIG. 1 illustrates a plurality of fiber forming units embodying the invention and an arrangement for collecting the fibers from the units in a fibrous mass;

FIG. 2 is a sectional view taken substantially on the line 2-2 of FIG. 1;

FIG. 3 is a vertical sectional view of one of the fiber forming units, the view being taken substantially on the line 33 of FIG. 1;

FIG. 4 is an enlarged fragmentary sectional view of a portion of the construction shown in FIG. 2, and

FIG. 5 is a fragmentary sectional view of a portion of the construction shown in FIG. 4, the view being taken substantially on the line 55 of FIG. 4.

Referring to the drawings in detail, and initially to FIG. 1 there is illustrated a melting and refining furnace 10 in which glass batch is conditioned by the application of heat to a molten or fiowable state and the fiowable glass refined in the furnace construction. Connected with the furnace 10 is a forehearth 12 having a forehearth channel 14 in which glass fiows from the furnace 10. Arranged along the bottom of the forehearth in spaced relation are stream feeders 16, each feeder flowing or delivering a stream 18 of glass from the forehearth channel 14. In the embodiment illustrated a fiber forming unit 20 is disposed beneath each stream feeder and each unit is adapted to receive a glass stream 18.

While FIG. 1 illustrates three fiber forming units 20, it is to be understood that a greater or lesser number of units may be employed depending upon the size or thickness of fibrous board or body formed from the collected fibers. Each fiber forming unit 20 is adapted for forming the glass of a stream 18 into discrete linear bodies or primary filaments by centrifuging the glass from a hollow spinner or rotor of comparatively large diameter, the primary filaments or bodies being attenuated to fibers by an annularly-shaped, high velocity gaseous blast.

The fiber forming units 20 are supported by conventional structural frame means (not shown). The attenuating region of each fiber forming unit is surrounded or embraced by a thin-walled cylindrically shaped guard 22 supported by brackets 23. As shown in FIG. 1, the blastattenuated fibers 24 from the fiber forming units are delivered into a rectangularly-shaped chamber or forming hood defined by a walled enclosure 26. Supported by each of the guard members 22 is a plurality of applicator nozzles 28 arranged in spaced circumferential relation for delivering binder or adhesive onto the fibers 24 in the chamber or hood 25.

Arranged at the base or open bottom of the walled enclosure 26 is the upper flight 30 of an endless belt fibercollecting conveyor 31. The conveyor is supported and guided by pairs of rolls 32, one of the rolls being driven by conventional motive means (not shown) to advance the upper flight 30 in a right-hand direction. Positioned beneath the upper flight 30 in registration with the chamber 25 is a suction chamber 34- defined by a thin-walled receptacle 36, the chamber 34 being connected by a pipe 37 with a suction blower of conventional construction (not shown) for establishing subatmospheric or reduced pressure in the chamber 34.

The reduced pressure or suction existent in the chamber 34 assists in the collection of the fibers 24 upon the conveyor flight 30, and the spent gases of the attenuating blasts are conveyed away through the pipe 37.

The fibers 24 accumulate in a mass 38, the flight 30 conveying the mass beneath a sizing or compression roll 40 which compresses the mass of fibers into a mat 42 of comparatively high density.

The dense mat of compressed fibers is conveyed by upper and lower endless belts 43 and 4 5 through an oven or curing chamber 48 in which the binder or adhesive on the fibers is cured or set by the application of heat and circulating air in the oven in a conventional manner. During the curing step the dense mat of fibers is maintained under constant compression so that upon curing or setting of the binder, the fibrous mat becomes a bonded, substantially rigid body or formboard 5%} of highly compressed fibers.

FIG. 3 illustrates in section a hollow spinner or rotor, a combustion burner arrangement providing a heated environment for the periphery of the rotor and the centrifuged primary filaments and a blower means for delivering an annular, high-velocity gaseous blast for attenuating the primary filaments projected from orifices in the rotor wall into fibers of varying lengths. The arrangement is inclusive of members or frame brackets 52 which support an annular combustion burner construction 54, the members 52 being welded as at 55 or otherwise secured to a circularly-shaped burner housing or casing 56.

The housing or casing 56 is configurated to provide an annularly-shaped manifold 57 having a threaded inlet fitting 63 adapted to be connected with tube means (not shown) for supplying a combustible mixture of fuel and air to the manifold 57. The combustion burner has an inner wall 58 concentric with the outer wall 59 of the burner casing 56, the outer wall 59 being joined with a substantially horizontal plate-like member 61 The wall 58 is of hollow construction providing a chamber 61 accommodating a circulating cooling fluid.

Arranged at the lower end of the inner wall 58 and welded or otherwise joined thereto is an annular plate or member 62. A depending circular lip or flange 64 on the plate 68 and an exterior surface 65 on the annular member 62 define an annular outlet or throat 66 for the burner. The region between the inner and the outer walls 58 and 59 contains refractory lining 68, the refractory being configurated to provide an annular combustion chamber or confined zone 70.

A plurality of circumferentially-spaced fittings 72 are disposed in openings in the refractory 68, the fittings 72 being fashioned with small passageways 74 through which fuel and air mixture from the manifold 57 is delivered into the combustion chamber 70. The mixture is ignited and burns within the combustion chamber or confined zone 70, and the intensely hot gases or products of coinbustion are delivered through the annular throat 66 to 1 provide a heated environment at the peripheral region of the spinner or rotor 76.

The hollow spinner 76 is fashioned with a hub portion 78, a peripheral wall portion 79, a web 80 joining the hub with the peripheral wall 79 and an inwardly extending flange 81 integrally joined with the lower end of the peripheral wall 79, the circular edge of the flange defining a circular opening 82. The hub portion 78 of the spinner is secured to a flange 84 on the lower end of a shaft or sleeve 85 by bolts 86.

The spinner 76 and the shaft or sleeve 85 are rotatably supported in anti-friction or ball bearings 88 disposed between the circular wall 58 of the burner casing and a second sleeve 90 surrounding the sleeve or hollow shaft 85. Mounted on the sleeve 90 is a sheave 92, secured to the sleeve 90 by a pin 93 or other securing means, the sheave 92 accommodating a driving belt 95, the belt engaging a pulley 96 mounted upon the armature shaft 98 of an electrically energizable motor 11)!) for rotating the sheave 92, the sleeve 90, the hollow shaft or sleeve 85 and the spinner 76.

The sleeve or tubular shaft 85 is slidably received within the sleeve 90 and an operative pin and slot arrangement (not shown) connects the hollow shaft 85 to the sleeve 90 to effect a drive between these components. The pin and slot driving connection is preferably of the character shown in the Kleist and Snow US. Pat. 2,962,- 754. Through the pin and slot connection, the hollow shaft 85 and the spinner 76 is removably carried by the sleeve 90.

Disposed within the spinner or rotor '76 is a means or distributor 104 for distributing the glass of a stream from a feeder 16 onto the inner peripheral surface of the peripheral wall 79 of the spinner. The distributor 104 is a cup-shaped member having a floor or bottom wall 106 and a peripheral wall 187, the latter having a plurality of openings 108 through which the heat-softened glass in the distributor is projected by centrifugal forces of rotation onto the interior surface of the peripheral spinner wall 79. The distributor 104 is equipped with a flange 110 secured to the hollow shaft or sleeve 85 by pins 111.

Mounted on the brackets or frame members 52 is a plate 114 which supports an annular member 115, the annular member 115 supporting an annular block 116 and a top plate 117 welded to the block. The block 116 and member 117 provide supporting means for three concentric sleeves 118, 119 and 120 forming components of a burner construction 122 disposed within the hollow shaft or quill 85 and a cooling jacket. Arranged between the lower end of sleeve 119 and the innermost sleeve 118 is an annular closure plate 124, the space between the sleeves 118 and 119 providing cooling jacket 126 through which water or other cooling fluid may be circulated in a conventional manner.

Secured to the lower ends of the sleeves 118 and 120 v is an annular orifice plate 128 having a plurality of small passages 130. The member or block 116 and the sleeve 119 define an annular manifold chamber 132, the member 116 having an opening accommodating a pipe 134 connected with a supply of combustible fuel and air mixture, the fuel and air mixture being delivered into the manifold chamber 132 and downwardly through the annular chamber 136 and through the passages 130.

The mixture is ignited at the outlets of the passages and is burned exteriorly of the plate 128 and above and interiorly of the distributor cup 104 to heat the glass in the distributor during start up and, if desired, may be used during normal operations to reduce heat losses. A valve (not shown) is connected with the mixture delivery pipe 134 to control the mixture supplied to the burner 122. The glass of the stream 18 flows by gravity through the passage 138 defined by the sleeve 118 and into the distributor cup 104.

The peripheral wall 79 of the spinner is preferably of a diameter of twelve inches or more and the peripheral wall area provided with a large number of small orifices or passages 140, there being at least ten thousand orifices and preferably approximately twelve thousand or more orifices through which the glass in the interior of the spinner is projected by centrifugal forces as small streams, linear bodies or primary filaments 142 as shown in FIG. 4.

The peripheral wall 79 of the spinner 76 is preferably slanted downwardly and inwardly with respect to the axis of rotation of the spinner, this angularity being indicated at 144 and is preferably between two and five degrees with respect to the axis of rotation of the rotor. The spinner is rotated to provide a peripheral linear speed preferably exceeding six thousand feet per minute for a twelve inch diameter rotor.

Means is provided for delivering an annular, highvelocity gaseous attenuating blast into engagement with the outwardly moving primary filaments or bodies 142 for attenuating the glass of the filaments to discrete fibers of varying lengths. In the method and apparatus of the invention a blast guiding or control surface means is configurated to establish a zone of reduced pressure and thereby cause turbulence in the gases of the attenuating blast, the turbulence causing the longer fibers to impinge the blast control surface or surface means and break up the long fibers into shorter lengths.

The arrangement includes a blower construction comprising an annular body having a cover member 152, the cover member being of annular configuration. The cover member 152 is secured to the body 150 by bolts 154 shown in FIG. 3. The blower body and cover member define an annular blower manifold 156 which is supplied with compressed air or steam under pressure from a supply.

The body 150 is fashioned with a frusto-conically shaped wall 158 and the cover member 152 provided with a depending circular flange 160, the portion of the body 150 adjacent the flange 160 being fashioned with a plurality of circumferentially-spaced slots 162 through which the compressed air or steam from the manifold chamber 156 is delivered in a downward direction as an annular high velocity attenuating blast. The frusto-conically shaped surface 158 is preferably of an inwardly and downwardly inclined angle of about twelve degrees with respect to the vertical axis of the spinner.

At a circular region 164 about three-eighths of an inch below an upper annular surface 165 of the blower body 150, the body is fashioned with a downwardly and in wardly inclined frusto-conically shaped blast control surface portion or section 168, the angularity being indicated at of about six degrees with respect to a vertical line AA, the latter being parallel with the axis of rotation of the spinner.

While a six degree angularity or taper of the frustoconically shaped control surface 168 with respect to the vertical axis of the spinner is quite effective in controlling or guiding adjacent gases of the blast, it is found that the surface 168 may be within an angular range or taper of from about three degrees to eight degrees and attain satisfactory operation. The blast control surface portion 168 extends to the lower surface 172 of the blower body 150, that is, about in a horizontal plane through the midregion of the peripheral wall 79 of the spinner.

The invention is inclusive of an extension member 174 for the blower construction having its upper surface 175 engaging and contiguous with the lower surface 172 of the blower body and is welded as at 176 or otherwise fixedly secured to the blower body 150. The extension member 174 is generally annular in shape provided with a circular recess or chamber 178, a circular plate being welded to the extension member 174 and providing a wall of the chamber 178. The chamber 178 accommodates a circulating fluid, such as water, the plate 180 being fashioned with fluid inlet and outlet connections (not shown).

The extension member 174 is fashioned with a blast guiding or control surface portion or section 182 of frustoconical shape, the surface 182 being downwardly and inwardly inclined toward the axis of the spinner. The angle indicated at 184 of the blast control or guiding surface 182 with respect to the vertical line A-A is preferably about three degrees for most efficient operation, but may be within a range of one degree to five degrees.

The upper edge 186 of the frusto-conical control surface 182 is of a diameter about one-eighth inch greater than the diameter of the edge 187, the circular edge 187 being at the juncture of the control surface 168 and the bottom surface 172 of the blower body 150.

Thus, the greater diameter of the edge 186 provides an overhanging annular lip or ledge 188 of about onesixteenth of an inch in width, as particularly shown in FIGS. 4 and 5. The gases of attenuating blast are projected downwardly from the slots 162 along the surface 158 thence along the control surface portion 168.

The ledge 188 provides a circular recess beneath the ledge and along the control surface portion 182 which allows abrupt expansion of the gases of the blast as they move below the edge 187. This region below the ledge or lip 188 provides a reduced pressure zone into which the adjacent gases of the blast expand abruptly and, the abrupt expansion effects turbulence in the gases along the control surface 182. The turbulence established in the gases of the attenuating blast below the ledge 188 cause the longer fibers being attenuated from the primary filaments 142 to be impinged against the control surface or surface portion 182, this action breaking up such longer fibers into shorter lengths.

The shorter length fibers are preferable in fashioning high density products such as roof boards or a wall board because the shorter length fibers provide less resiliency and hence more rigidity and strength in a high density substantially rigid board-like end product. Another function of the control surface or surface section 182 is to confine the attenuated fibers and thereby effect concentration of the fibers at the fiber deposition or collection zone on the conveyor flight 30.

While it has been found that the angularity or taper of the control surface 182 for most effective functioning of the surface should be about three degrees, the surface 182 may be within a range of one degree to five degrees depending upon the velocity of the attenuating blast and the degree to which it is desired to break up longer fibers and the extent that it is desired to confine the fibers by the frusto-conical control surface 182.

While it has been found that the ledge or overhanging lip 188 of the blower skirt of about one-sixteenth of an inch in width is effective in producing the desired turbulence beneath the ledge to break up or fracture the longer fibers, it is to be understood that the ledge may be of slightly greater width if it is desired to provide increased turbulence in the gases of the blast beneath the ledge 188. It is further found that the width of the ledge 188 is of a critical nature in effecting turbulence in the gases of the blast and should be maintained in a range of between .060 and .075" in width.

As the ledge 188 is of annular character, the diameter of the surface portion 182 at the edge 186 is in a range of from .120 and .150" greater than the diameter of the edge 187 at the lower end of the control surface portion 168. It is also found that the ledge 188 must be an abrupt offset in order to promote proper turbulence in the adjacent gases of the blast to effect fracture of the longer fibers.

Thus, the control surface 182 of the extension 174 of the blower skirt arrangement is essential to effect a fracturing of the longer fibers into shorter lengths for the fabrication of fibrous products of high densities.

Without the control surface 182 there is no appreciable fracturing of longer fibers in the blast and hence a product made from the longer fibers is endowed with a degree of resilience which must be avoided in high density products such as roof boards and wall boards fashioned of compressed glass fibers. The fibers for such products are 7 usually compressed to densities in a range of from five to twelve pounds per cubic foot.

The method and apparatus employed with a large diameter spinner, viz. a diameter of about twelve inches provides a high yield of fibers of lengths particularly usable in the formation of high density products. It has been found preferable to fashion the blower skirt extension or member 174- of stainless steel in order to minimize wear resulting from high velocity impingement of the fibers against the blast control or guide surface 182.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

I claim:

1. Apparatus of the character disclosed, in combination, a hollow spinner having a peripheral wall provided with a plurality of orifices, means for Supplying heatsoftened glass to the spinner, means for rotating the spinner to project the glass through the orifices by centrifugal forces forming primary filaments, a blower construction including a manifold surrounding the spinner, said manifold having passages through which gas from the manifold is delivered as a high velocity blast into engagement with the primary filaments of glass for attenuating the primary filaments to discrete fibers, blast control surface means provided on the blower construction, said blast control surface means including two frusto-conically shaped surfaces downwardly and inwardly inclined toward the axis of the spinner, one frusto-conically shaped surface being below the gas delivery passages and above the other frusto-conically shaped surface, the lower edge of the upper surface being of lesser diameter than the diameter of the upper edge of the lower surface, said blower construction having a substantially horizontal annular surface joining said edges of the frusto-conically shaped surfaces, the width of the annular surface being in a range of sixty thousandths of an inch and seventyfive thousandths of an inch, the region beneath the annular surface providing a zone of reduced pressure influencing the direction of movement of gases of the attenuating blast to cause fibers to impinge the lower frusto-conically shaped surface.

2. Apparatus of the character disclosed, in combination, a hollow spinner having a peripheral wall provided with a plurality of orifices, means supplying heat-softened glass to the spinner, means for rotating the spinner to project the glass through the orifices by centrifugal force forming primary filaments, a blower construction including a manifold surrounding the spinner, said manifold having passages through which gas from the manifold is delivered as a high velocity blast into engagement with the primary filaments of glass for attenuating the filaments to discrete fibers, said blower construction having a first downwardly and inwardly inclined frusto-conically shaped blast-guiding surface disposed below the gas delivery passages, a second downwardly and inwardly inclined frusto-conically shaped surface disposed beneath the first blast guiding surface, the lower terminal edge of the upper frustoconically shaped surface being of lesser diameter than the upper terminal edge of the lower frusto-conically shaped surface, said terminal edges being in a horizontal plane passing through the mid region of the peripheral wall of the spinner, said blower construction having an annular horizontal surface in said plane providing a ledge between the surfaces, said ledge being of a width in a range of sixty thousandths of an inch and seventy-five thousandths of an inch, the enlarged region beneath the ledge establishing turbulence in the gases of the blast to impinge the fibers upon the second frusto-conically shaped surface section to fracture fibers into shorter lengths.

3. Apparatus of the character disclosed, in combination, a hollow spinner having a peripheral wall provided with a plurality of orifices, means for supplying heatsoftened glass to the spinner, means for rotating the spinner to project the glass through the orifices by centrifugal force forming primary filaments, a blower construction including a manifold surrounding the spinner, said manifold having passages through which gas from the manifold is delivered as a high velocity blast into engagement with the primary filaments of glass for attenuating the filaments to discrete fibers, said manifold having a first frusto-conically shaped surface inclined downwardly and inwardly toward the axis of the spinner, said frustoconically shaped surface being disposed below the gas delivery passages, an extension member engaging and disposed below the manifold and having a second downwardly and inwardly inclined frusto-conically shaped surface disposed beneath the first frusto-conically shaped surface, the lower terminal edge of the first frusto-conically shaped surface being of lesser diameter than the upper terminal edge of the second frusto-conically shaped surface, said terminal edges being in a horizontal plane passing through the mid region of the peripheral wall of the spinner, said manifold having an annular horizontal surface in said plane providing a ledge between the surfaces, said ledge being of a width in a range of sixty thousandths of an inch and seventy-five thousandths of an inch, the region beneath the ledge providing a reduced pressure zone establishing turbulence in gases of the blast to impinge the fibers upon the second frustoconically shaped surface.

4. The combination according to claim 3 wherein the extension member is fashioned of stainless steel and shaped to provide a chamber accommodating cooling fluid.

References Gited UNITED STATES PATENTS 2,136,158 11/1938 Thomas 5 2,982,991 5/1961 Karlovitz 65-16X 3,019,477 2/1962 Kleist 6514 S. LEON BASHORE, Primary Examiner R. L. LINDSAY, JR. Assistant Examiner US. Cl. X.R. 656; 26412 

